The invention relates to a safety system and method for a vehicle using a toxic and/or combustible fuel which can form an ignitable mixture with ambient air and, more particularly, to a vehicle safety system which uses sensors mounted in closed spaces of the vehicle to measure fuel concentrations at points where harmful gases collect and to generate signals for opening and closing certain spaces in the vehicle to dissipate the concentrations.
The use of gas sensors in passenger compartments is known, for example, from DE-OS 35 05 670. However, these gas sensors are designed to shut off the air supply to the vehicle interior when an increased concentration of harmful substances exists outside the vehicle. Such sensors do not take into account that fuels carried in the vehicle gas tank may emerge from the tank and form toxic and/or inflammable gas concentrations in the vehicle interior or in the trunk.
It is an object of the present invention to provide a vehicle safety system and method which increases the operating safety of the vehicle and protects particularly against the formation of combustible gas concentrations in the closed spaces of the vehicle.
The foregoing object is achieved in accordance with the present invention through the provision of at least one sensor mounted in the closed spaces of the vehicle at a point which, because the physical characteristics of the fuel as well as of the spatial conditions of the vehicle, harmful substances and/or gases collect initially, and at least one sensor for measuring the harmful substance concentration in the outside or ambient air such that the sensors generate signals which through conventional electronic control circuitry can be used to open and close vehicle spaces depending upon the type of harmful substance or gas concentration.
By virtue of the safety system of the present invention, large amounts of fuel which, together with the ambient air, form a combustible mixture in closed spaces, may be discharged relatively rapidly and without danger into the ambient air where they become harmless very rapidly.
By avoiding a total encapsulation of the fuel system and a gastight encapsulation of the passenger compartment, significant advantages are achieved with respect to cost and weight. The sealing off of the passenger compartment with respect to the trunk takes place as a result of weighing costs and benefits.
The safety system of the present invention is useful particularly in cases where the fuel cannot be detected by human sensory organs, for example, in the case of hydrogen which is tasteless, odorless and colorless. In addition, in comparison with conventional hydrocarbon-containing fuels, hydrogen has a substantial safety disadvantage because of its wide ignition range in air and low ignition energy. As a result of the supply of fresh outside air into the otherwise essentially closed spaces of the vehicle, i.e., the passenger compartment and the trunk, the hydrogen concentration in the vehicle spaces remains, on the average, below the lower ignition limit which is at approximately 4% hydrogen in air.
Since hydrogen is approximately 15 times lighter than air and therefore has a corresponding rise rate or lift, a sensor is arranged in accordance with the present invention above the fuel tank in the passenger compartment at the ceiling and in the trunk proximate to the fuel tank at the highest point of the trunk covering. If the escaping fuel will form a gas in the ambient air which is heavier than air, however, the sensors should be arranged in proximity to the vehicle floor.
The safety system of the present invention may also be used where the outside air surrounding the vehicle has a high concentration of harmful substances so that the protection device of the subject safety system automatically, as a function of the oxygen content in the passenger compartment, temporarily closes the inlet and outlet ventilation openings of the vehicle when a permissible concentration of harmful substances is exceeded. Furthermore, ventilation of the passenger compartment or of the trunk may be increased by using a fan or a ventilator.
Simultaneously with the fresh air supply into the otherwise closed spaces of the vehicle, the fuel removal from the tank of the leaky fuel supply system is shut off and changeover can occur to a second fuel supply system. As a result of changing over to a second fuel supply system, it is possible with the present invention to steer the vehicle without any power disruption out of a possible danger zone.
In order to avoid the risk of explosion in the case of collisions, an acceleration sensor is arranged at the vehicle which, when an impermissibly high acceleration is exceeded, emits a signal by way of an electronic circuit and appropriate control devices, unlocks the doors and opens the side windows, the sliding roof, and the trunk lid.
It is also an advantage of the present invention that, in the case of an excessive deformation of the vehicle rear, the trunk lid will open up without any use of driving motors and solely as a result of trunk lid construction. This opening may be achieved, for example, by a special design of the trunk lid lock which may, have a predetermined breaking point and/or in which the locking part is swivelled in the direction of the passenger compartment in the case of an excessive deformation. Other constructional alternatives include the shape of the trunk lid and the arrangement of springs at the pivotal connecting points of the trunk lid.
It is also an advantage that a battery used as voltage supply point for the safety system is not excessively drained by the protection device so that the protection device can operate continuously even during fairly long stoppage or parking times of the vehicle. Should for any reason the supply voltage fall below a selected value, the trunk lid, the side windows, the sliding roof, etc., will be opened automatically.
In order to draw the driver's immediate attention to the occurrence of critical gas concentrations, the protection device has visual and acoustic warning devices. These warning signals may, however, be emitted as early as before the opening of the windows, etc., so that undesired reflex actions by the driver are avoided. Correspondingly, at the start of the ventilation of the passenger compartment, the rear side windows may be opened first.
The components of the electronic circuit used for controlling the safety of the present invention are relatively small and easy to handle so that a simple and compact housing of the circuit components in the interior of the vehicle is possible. It is also an advantage that the safety system can easily be connected to the cable harness and the electronic system of the vehicle so that no additional lines must be laid for the control, for example, of the electric motors for the actuation of the sliding rood or of the windows.
In addition, the vehicle contains a valve block which is arranged outside the tank and which comprises all solenoid valves and flap valves required for inertization, refueling and engine supply. As a result of the arrangement of a valve block outside the tank, the entering of heat into the tank is minimized and servicing is facilitated. In addition, short line lengths between the valves reduce dead spaces where dirt may collect, and furthermore, the short line lengths reduce evaporation losses during the refuelling operation. Finally, gaseous hydrogen can be discharged into the open air by way of the valve block.